• 대한임베디드공학회논문지
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• 제6권6호
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• pp.369-376
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• 2011

Since wireless sensor networks generally have the capability of network recovery, malfunction of a few sensor nodes in a sensor network does not cause a crucial problem paralyzing the sensor network. The malfunction of the sink node, however, is critical. If the sink node of a sensor network stops working, the data collected by sensor nodes cannot be delivered to the gateway because no other sensor nodes can take the place of the sink node. This paper proposes a TDMA-based wireless sensor network equipped with dual sink nodes, with a view to preventing data loss in the case of malfunction of a sink node. A secondary sink node, which synchronizes with a primary sink node and receives data from other sensor nodes in normal situations, takes the role of the primary sink node in the case of malfunction of the primary sink, thereby eliminating the possibility of data loss. The effectiveness of the proposed scheme is demonstrated through experiments.

• 비파괴검사학회지
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• 제31권6호
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• pp.616-625
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• 2011

Ensuring the designed prestress force is very important for the safety of prestressed concrete bridge. The loss of prestress force in tendon could significantly reduce load carrying capacity of the structure. In this study, an automated prestress-loss monitoring system for prestressed concrete girder using PZT-interface and wireless impedance sensor node is presented. The following approaches are carried out to achieve the objective. Firstly, wireless impedance sensor nodes are designed for automated impedance-based monitoring technique. The sensor node is mounted on the high-performance Imote2 sensor platform to fulfill high operating speed, low power requirement and large storage memory. Secondly, a smart PZT-interface designed for monitoring prestress force is described. A linear regression model is established to predict prestress-loss. Finally, a system of the PZT-interface interacted with the wireless sensor node is evaluated from a lab-scale tendon-anchorage connection of a prestressed concrete girder.

• 센서학회지
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• 제16권5호
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• pp.361-368
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• 2007

Small size real-time ECG signal analysis function by QRS-complex detection was put into sensor nodes. Wireless sensor nodes attached on the patient’s body transmit ECG data continuously in normal u-healthcare system. So there are heavy communication traffics between sensor nodes and gateways. New developed platform for real-time analysis of ECG signals on sensor node can be used as an advanced diagnosis and alarming system for healthcare. Sensor node does not need to transmit ECG data all the time in wireless sensor network and to server PC via gateway. When sensor node detects suspicion or abnormality in ECG, then the ECG data in the network was transmitted to the server PC for further powerful analysis. This system can reduce data packet overload and save some power in wireless sensor network. It can also increase the server performance.

• Journal of information and communication convergence engineering
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• 제9권6호
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• pp.676-682
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• 2011

Sybil attack can disrupt proper operations of wireless sensor network by forging its sensor node to multiple identities. To protect the sensor network from such an attack, a number of countermeasure methods based on RSSI (Received Signal Strength Indicator) and LQI (Link Quality Indicator) have been proposed. However, previous works on the Sybil attack detection do not consider the fact that Sybil nodes can change their RSSI and LQI strength for their malicious purposes. In this paper, we present a Sybil attack detection method based on a transmission power range. Our proposed method initially measures range of RSSI and LQI from sensor nodes, and then set the minimum, maximum and average RSSI and LQI strength value. After initialization, monitoring nodes request that each sensor node transmits data with different transmission power strengths. If the value measured by monitoring node is out of the range in transmission power strengths, the node is considered as a malicious node.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 추계종합학술대회
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• pp.518-521
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• 2007

TinyOS기반의 u-헬스케어를 위한 무선센서노드 어플리케이션을 구현하였으며 이를 이용하여 기존의 지속적인 데이터 전송방식과 성능 비교를 하였다. 무선센서노드에서 QRS-complex 넓이와 R-R간격을 이용하여 비정상적인 ECG를 감지하였다. 사용된 ECG 데이터는 MIT/HIB Database 100, 112, 119번을 이용하였다. 정상적인 ECG 데이터를 가지고 있는 100레코드를 기준으로 지속적인 데이터 전송 시 발생되는 패킷량과 전원 소모율을 측정 후, 본 연구에서 구현된 문선센서노드 어플리케이션을 이용하여 각각의 ECG데이터를 이전과 같은 방법으로 성능 평가하여 비교분석 하였다. 비교분석 결과, ECG 데이터 발생량, 전원 소모율이 획기적으로 감소된 것을 알 수 있었다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 추계학술대회
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• pp.1035-1037
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• 2009

고정노드를 사용하는 일반적인 센서 네트워크와 달리 최근의 무선 센서 네트워크에서는 노드의 이동이 빈번히 일어난다. 이러한 무선 센서 네트워크에서는 센서노드의 이동성을 고려하여 동적으로 자가구성이 가능한 라우팅 프로토콜이 요구된다. 본 논문에서는 고정 노드에서의 자가구성과 에너지효율성이 유용한 LEACH 프로토콜을 기반으로 하여 노드의 이동에 따라 클러스터가 동적으로 자가 구성되는 M-LEACH 라우팅 프로토콜을 제안한다.

• 센서학회지
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• 제16권4호
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• pp.247-253
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• 2007

Low power consumption sensor network platform (sensor node) for sensor networking with IEEE 802.15.4 protocol was fabricated. The sensor node used ceramic bar type antenna for increasing RF signal performance and decreasing PCB size occupied by antenna. The communication range of the fabricated sensor node was about $20{\sim}30$ m in open environment with 915 MHz frequency bandwidth and well supported by Tiny OS. The sensor node have good connectivity with various external devices by RS-232, I2C, analogue and digital expansion board, hence, this sensor node can be applied to various applications in wireless sensor network and ubiquitous sensor network.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권10호
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• pp.4223-4249
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• 2015

A novel jamming detection technique to detect the presence of jamming in the downstream direction for cluster based wireless sensor networks is proposed in this paper. The proposed technique is deployed in base station and in cluster heads. The proposed technique is novel in two aspects: Firstly, whenever a cluster head receives a packet it verifies whether the source node is legitimate node or new node. Secondly if a source node is declared as new node in the first step, then this technique observes the behavior of the new node to find whether the new node is legitimate node or jammed node. In order to monitor the behavior of the existing node and new node, the second step uses two metrics namely packet delivery ratio (PDR) and received signal strength indicator (RSSI). The rationality of using PDR and RSSI is presented by performing statistical test. PDR and RSSI of every member in the cluster is measured and assessed by the cluster head. And finally the cluster head determines whether the members of the cluster are jammed or not. The CH can detect the presence of jamming in the cluster at member level. The base station can detect the presence of jamming in the wireless sensor network at CH level. The simulation result shows that the proposed technique performs extremely well and achieves jamming detection rate as high as 99.85%.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권10호
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• pp.2529-2547
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• 2012

In this paper, we use a quadrotor-based mobile sink to gather sensor data from the terrestrial deployed wireless sensor network. By analyzing the flight features of the mobile sink node, we theoretically study the flight constraints of height, velocity, and trajectory of the mobile sink node so as to communicate with the terrestrial wireless sensor network. Moreover, we analyze the data amount which the mobile sink can send when it satisfies these flight constraints. Based on these analysis results, we propose a data acquisition approach for the mobile sink node, which is discussed detailed in terms of network performance such as the transmission delay, packet loss rate, sojourning time and mobile trajectory when given the flying speed and height of the mobile sink node. Extensive simulation results validate the efficiency of the proposed scheme.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 추계학술대회
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• pp.585-588
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• 2009

무선센서네트워크는 처리능력과 자원이 제한된 수많은 소형의 센서노드들로 구성된다. 따라서 무선센서네트워크에 있어서 가장 중요하고 기본적인 요소는 환경 정보를 수집하고 이를 사용자 응용시스템에 전송하는 센서노드 기술이다. 기술의 발전에 따라 센서노드는 점점 소형화 되고 지능화 되어 그 응용범위를 넓혀가고 있다. 특히 이식형 센서노드 기술은 인체나 가축의 체내에 이식되어 질병을 감시하고 치료하는데 사용됨으로써 무선센서네트워크의 미래 발전 방향을 제시한다. 본고에서는 가축의 체온을 실시간으로 감시할 수 있는 이식형 무선 센서노드를 설계하였다. 또한, 실시간 생체 감시 시스템 구현을 위한 추가적인 고려사항에 대하여 논하였다.